debugobjects: Rework free_object_work()

Convert it to batch processing with intermediate helper functions. This
reduces the final changes for batch processing.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com>
Link: https://lore.kernel.org/all/20241007164914.015906394@linutronix.de

diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 3700ddf..d5a8538 100644 (file)
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -35,7 +35,7 @@
  * frequency of 10Hz and about 1024 objects for each freeing operation.
  * So it is freeing at most 10k debug objects per second.
  */
-#define ODEBUG_FREE_WORK_MAX   1024
+#define ODEBUG_FREE_WORK_MAX   (1024 / ODEBUG_BATCH_SIZE)
 #define ODEBUG_FREE_WORK_DELAY DIV_ROUND_UP(HZ, 10)
 
 struct debug_bucket {
@@ -158,6 +158,21 @@ static bool pool_move_batch(struct obj_pool *dst, struct obj_pool *src)
        return true;
 }
 
+static bool pool_pop_batch(struct hlist_head *head, struct obj_pool *src)
+{
+       if (!src->cnt)
+               return false;
+
+       for (int i = 0; src->cnt && i < ODEBUG_BATCH_SIZE; i++) {
+               struct hlist_node *node = src->objects.first;
+
+               WRITE_ONCE(src->cnt, src->cnt - 1);
+               hlist_del(node);
+               hlist_add_head(node, head);
+       }
+       return true;
+}
+
 static struct debug_obj *__alloc_object(struct hlist_head *list)
 {
        struct debug_obj *obj;
@@ -343,55 +358,36 @@ static struct debug_obj *alloc_object(void *addr, struct debug_bucket *b,
        return obj;
 }
 
-/*
- * workqueue function to free objects.
- *
- * To reduce contention on the global pool_lock, the actual freeing of
- * debug objects will be delayed if the pool_lock is busy.
- */
+/* workqueue function to free objects. */
 static void free_obj_work(struct work_struct *work)
 {
-       struct debug_obj *obj;
-       unsigned long flags;
-       HLIST_HEAD(tofree);
+       bool free = true;
 
        WRITE_ONCE(obj_freeing, false);
-       if (!raw_spin_trylock_irqsave(&pool_lock, flags))
-               return;
 
-       if (pool_global.cnt >= pool_global.max_cnt)
-               goto free_objs;
-
-       /*
-        * The objs on the pool list might be allocated before the work is
-        * run, so recheck if pool list it full or not, if not fill pool
-        * list from the global free list. As it is likely that a workload
-        * may be gearing up to use more and more objects, don't free any
-        * of them until the next round.
-        */
-       while (pool_to_free.cnt && pool_global.cnt < pool_global.max_cnt) {
-               obj = hlist_entry(pool_to_free.objects.first, typeof(*obj), node);
-               hlist_del(&obj->node);
-               hlist_add_head(&obj->node, &pool_global.objects);
-               WRITE_ONCE(pool_to_free.cnt, pool_to_free.cnt - 1);
-               WRITE_ONCE(pool_global.cnt, pool_global.cnt + 1);
-       }
-       raw_spin_unlock_irqrestore(&pool_lock, flags);
-       return;
+       if (!pool_count(&pool_to_free))
+               return;
 
-free_objs:
-       /*
-        * Pool list is already full and there are still objs on the free
-        * list. Move remaining free objs to a temporary list to free the
-        * memory outside the pool_lock held region.
-        */
-       if (pool_to_free.cnt) {
-               hlist_move_list(&pool_to_free.objects, &tofree);
-               WRITE_ONCE(pool_to_free.cnt, 0);
+       for (unsigned int cnt = 0; cnt < ODEBUG_FREE_WORK_MAX; cnt++) {
+               HLIST_HEAD(tofree);
+
+               /* Acquire and drop the lock for each batch */
+               scoped_guard(raw_spinlock_irqsave, &pool_lock) {
+                       if (!pool_to_free.cnt)
+                               return;
+
+                       /* Refill the global pool if possible */
+                       if (pool_move_batch(&pool_global, &pool_to_free)) {
+                               /* Don't free as there seems to be demand */
+                               free = false;
+                       } else if (free) {
+                               pool_pop_batch(&tofree, &pool_to_free);
+                       } else {
+                               return;
+                       }
+               }
+               free_object_list(&tofree);
        }
-       raw_spin_unlock_irqrestore(&pool_lock, flags);
-
-       free_object_list(&tofree);
 }
 
 static void __free_object(struct debug_obj *obj)